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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

GIACIATION OF THE YAKUTAT BAY REGION
223
moraine above fiord bottom is at least 281 feet on one side and 216 on the other. The inferred conditions in southern Russell Fiord before, during, and since the building of this submerged moraine are shown in the three maps of PI. XCJIE. If this is wholly a moraine the ice must have halted here a long time, for accumulation under water must be very slow indeed.
In outer Yakutat Bay the great shoal at the entrance is surely morainic, and there may be a second moraine below sea level northwest of Knight Island (Fig. 21) as Gilbert has shown.1 It is of interest to compare this outermost moraine of the Malaspina -Disenchantment Bay Glacier with the outermost moraine of the Russell Fiord Glacier. The former (Fig. 21) is two or three miles wide, rising 800 to 400 feet above the bottom of the inner bay, and sloping steeply seaward on the Pacific side, where there is no marked convexity. This contrasts with the Russell Fiord terminal moraine whose inner face is revealed by the soundings in 1910 (PI. XCH). The Russell Fiord moraine is nearly twice as wide, rising to approximately 200 feet above sea level, or 275 to 980 feet above the bottom of the expanded end of Russell Fiord. It is markedly
convex seaward and is bordered by a gently-sloping outwash plain. Because the glacier was not cut back by the ocean waves and melted back by the salt water it had the form of a bulb-glacier.
Other topographic features suggestive of either moraines below sea level or ridges between rock rimmed basins of the fiord bottom (PL XCI) are (1) near Shelter Cove in southern Russell Fiord; (2) between Seal Bay and Cape Enchantment; and (3) immediately east of the lip of the hanging valley of Nunatak Fiord. In each case the topographic form of the fiord bottom indicates either a morainic shoal or an irregularity in glacial sculpture. The first of these shoals rises 75 to 100 feet above the general fiord
> Gilbert, G. K., Harriman Alaska Expedition, Vol. m. 1904, pp. 49-60.
FIG. 21. YAKUTAI BAT, SHOWING CONTOURS OF DEPTH AND SUBMARINE MORAINE BETWEEN OCEAN CAPE AND POINT MANBY (Arrxra G. K. GILBERT).